Renewal of support for five years is requested for a program of research related to injury of neurons of the vertebrate spinal cord. The general goal of this program project continues to be to gain insight into the nature of the fundamental mechanisms associated with regeneration of neurites and/or functional recovery after injury to spinal cord neurons. The projects address issues ranging from functional recovery in cold blooded vertebrates to mammalian models of clinical syndromes. The projects are multidisciplinary in approach, combining physiological. morphological and histochemical/molecular techniques. Most of the projects derive from results obtained during previous years of support. Three of the projects (2, 3, and 6) are directed at the nature or basis of changes in motor function, skeletal or autonomic, after injury of spinal neurons. Two projects (1 and 2) concern the mechanisms of altered sensory function following injury to central or peripheral afferent pathways. One project (5) examines the possibility that causalgic states following peripheral nerve injury may result from altered interactions between sympathetic efferents and nociceptive afferents. While each of the six projects will be carried out by an independent team of investigators, the teams share a common interest in the consequences of injury to spinal neurons, use many of the same techniques, and depend on core facilities to accomplish their research goals.